I, Frank Seth Gaunce, have invented a system to prevent portable water distribution systems from corrosion by the protective concentration of disinfecting chemicals that are intentionally left in the potable water to protect it during its delivery to point of use. Typically, the distribution systems are comprised of an iron main and distribution lateral of lead or copper, to point of use.
The disinfecting chemicals (disinfectants) will corrode all the metals of the distribution systems, even at the low protective concentrations (<1 to 4 PPMs) of disinfectants. The metals are corroded in the order: iron, lead, copper, which is the order of their metal reduction potentials. So long as they are electrically connected, the top metal will prevent the corrosion of all of the metals lower in the sequence. Lead and copper, are not protected, electro-chemically, from corrosion by the disinfectants, when the iron mains are removed or corroded away and replaced with plastic mains.
With the lead pipes, the corrosion is over the entire interior surface, and is evidenced by an unacceptable increase of the lead concentration in the delivered portable water. In the case of copper, the corrosion tends to be very local, resulting in pipe pinhole water leaks.
Where the iron mains are replaced with electrically non-conducting plastic mains the copper and the lead laterals are corroded, but can be protected by providing a potential source of at least the equivalent of the reduction potential of iron. In the case of lead, the corrosion will stop and the lead contamination of the potable water will cease. In the case of copper, the copper corrosion will cease but the corroded pinholes remain necessitating a repair action before the lateral can be used to deliver water.
At this time the generally accepted method to deal with pinholes in copper plumbing is to replace the copper plumbing with plastic plumbing. This is a very invasive and costly action which has negative, but generally acceptable consequences. It reduces the maximum allowable operating pressure of the system. It also removes from the system the desirable anti-bacteria characteristic of copper.